When slaughtering animals, such as cattle, small livestock and poultry, it is customary, after the animal has been stunned or killed, to open one or more important blood vessels and to allow the blood to run out of the animal. The blood vessel which is to be opened is usually the carotid artery. In order to ensure that the blood runs out of the animal as fully as possible, it is moved into a position which is such that the sticking location is located at a lower level than most of the rest of the body of the animal. In specific terms, this usually means that the animal is hung by at least one leg, in particular—other than in the case of poultry—by at least one hind leg.
In the case of animals which have been stunned electrically or with the aid of a gas atmosphere, a heart beat, muscle reactions and a pump action are still present in the blood vessels sometime after sticking, and all these actions promote exsanguination of the slaughter animal. In the case of animals which are already substantially dead before the blood vessels are opened, the heart beat, muscle reactions and pump action in the blood vessels are substantially absent, so that apart from the external application of pressure to the body of the animal, it is only possible to use the force of gravity for the exsanguination process.
In the case of stunned animals, but even more so in the case of dead animals (owing to the corporeal functions which are then absent), it is important for the blood vessels to be opened as fully as possible. The current state of the art includes various devices which can be used to open the blood vessels in the neck of poultry.
European Patent No. 262,289 describes a device in which a fowl which is hung by its legs is moved onwards. The neck of the fowl is fixed between two substantially fork-like supports, the limbs of the supports being directed towards one another. While the neck of the poultry is being fixed in place, a double blade, which is provided with a substantially U-shaped recess, is stuck into the neck at the front side of the neck, transversely with respect to the longitudinal direction of the neck, with the result that the two carotid arteries are opened. The U-shaped recess is intended to prevent the blade from damaging the cervical vertebrae, the oesophagus or the trachea in the neck of the poultry.
U.S. Pat. Nos. 4,354,296 and 5,425,668 describe opening a jugular vein of poultry with the aid of a rotating blade at the side of the neck and with the aid of a device in which the poultry is moved onwards hanging by its legs.
U.S. Pat. No. 4,392,273 describes a device in which the head of poultry which is suspended by its legs and moved onwards by the device is trapped between two parallel, helical and rotating guides, which are provided, on their outlet side, with blades which are directed towards one another, for opening the jugular veins at the sides of the neck.
A problem which arises in particular when dead animals are being exsanguinated with the aid of the force of gravity is presented by the inaccessibility of the arteries in the neck when using the conventional methods of opening blood vessels with the aid of a rotating blade. The arteries are located relatively far from the surface of the neck, and to achieve optimum exsanguination of the slaughter animal, should also be opened in addition to the veins. However, with the conventional means this is impossible without also cutting into or severing the oesophagus and/or the trachea. This is sometimes undesirable, since in a later stage of the processing of the slaughter animal it is often necessary for the connections between the head of the slaughter animal and its body, which are formed in particular by the trachea and the oesophagus, to be intact, so that these connections can be pulled out at the head, and any organs which are joined to them can be pulled out of the body of the slaughter animal.
Another problem in the prior art is the fact that opening a blood vessel in the neck of a slaughter animal which is hung by a (hind) leg immediately causes a large amount of blood to emerge from the neck, which blood contaminates the device used for opening to a considerable extent. To combat the negative consequences of this contamination, such as bacterial infection, continuous, intensive cleaning of the device is required.